Abstract
BackgroundRenewable chemicals have attracted attention due to increasing interest in environmental concerns and resource utilization. Biobased production of industrial compounds from nonfood biomass has become increasingly important as a sustainable replacement for traditional petroleum-based production processes depending on fossil resources. Therefore, we engineered an Enterobacter cloacae budC and ldhA double-deletion strain (namely, EC∆budC∆ldhA) to redirect carbon fluxes and optimized the culture conditions to co-produce succinic acid and acetoin.ResultsIn this work, E. cloacae was metabolically engineered to enhance its combined succinic acid and acetoin production during fermentation. Strain EC∆budC∆ldhA was constructed by deleting 2,3-butanediol dehydrogenase (budC), which is involved in 2,3-butanediol production, and lactate dehydrogenase (ldhA), which is involved in lactic acid production, from the E. cloacae genome. After redirecting and fine-tuning the E. cloacae metabolic flux, succinic acid and acetoin production was enhanced, and the combined production titers of acetoin and succinic acid from glucose were 17.75 and 2.75 g L−1, respectively. Moreover, to further improve acetoin and succinic acid production, glucose and NaHCO3 modes and times of feeding were optimized during fermentation of the EC∆budC∆ldhA strain. The maximum titers of acetoin and succinic acid were 39.5 and 20.3 g L−1 at 72 h, respectively.ConclusionsThe engineered strain EC∆budC∆ldhA is useful for the co-production of acetoin and succinic acid and for reducing microbial fermentation costs by combining processes into a single step.
Highlights
Renewable chemicals have attracted attention due to increasing interest in environmental concerns and resource utilization
The results indicated that elimination of 2,3-butanediol and lactic acid formation in the EC∆budC∆lactate dehydrogenase (ldhA) strain led to enhanced acetoin and succinic acid co-production, and the maximum acetoin and succinic acid yields were obtained as 0.397 and 0.046 mol mol−1 glucose, respectively
The results indicated that the acetoin and succinic acid co-production of the EC∆budC∆ldhA strain was improved by fed-batch fermentation
Summary
Renewable chemicals have attracted attention due to increasing interest in environmental concerns and resource utilization. Biobased production of industrial compounds from nonfood biomass has become increas‐ ingly important as a sustainable replacement for traditional petroleum-based production processes depending on fossil resources. Acetoin is an intermediate product of the 2,3-butanediol biosynthesis pathway [7]. It is produced from pyruvate through α-acetolactate by two enzymes, including α-acetolactate synthase (budB) and α-acetolactate decarboxylase (budA), and converted to 2,3-butanediol by 2,3-butanediol dehydrogenase (budC) with the consumption of NADH [8]. Several studies have reported that the deletion of 2,3-butanediol dehydrogenase (budC) improves the production of acetoin in different species of microorganisms [2, 3, 9, 10]
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